Ubiquitin Activating Enzyme E1 [UBA1] (human) (rec.) (His)

UBA1, the canonical ubiquitin E1 activating enzyme is a 118kDa protein, which forms a homodimer in its active state and catalyzes the first step of the ubiquitin conjugation cascade. It activates ubiquitin in an ATP-dependent mechanism where ATP is hydrolyzed to AMP and PPi, a ubiquitin C-terminal adenylate intermediate is formed, then transferred to the E1's active site cysteine through a thioester bond. This thioester is then transferable to an E2 conjugating enzyme's active site cysteine.